Updated changelog and bumped version up to 0.20.0
Fix version_info typo in setup.py
Add requirements_rtd.txt to MANIFEST.in to fix potential packaging issues with 2.7
Merge branch 'develop' into release/0.20.0
Updated changelog with last minute change.
Merge branch 'develop' into release/0.20.0
Make v0.9.17 model a 2.7-compatible pickle.
Make v0.9.17 model a 2.7-compatible pickle for real this time.
Added Python 2 AND 3 compatible models, since pickles can't be shared across versions.
Fix missing sys import (this is getting ridiculous).
Fix pickled models having the wrong names for unit test. (The Python 2 and 3 model names were swapped.)
Merge branch 'release/0.20.0' into develop